Rubbing seal system for a rotary combustion engine

ABSTRACT

A sealing assembly is disclosed for use in providing a dynamic seal between a rotor and the surrounding housing of a rotary internal combustion engine. An apex seal of considerable height is arranged to fit within a first receptacle in at least one location along the periphery of the rotor; the apex seal has a transverse opening separating the body of the seal into first and second support portions. A second receptacle is defined about the ends of the first receptacle for receiving a corner seal adapted to engage the side housing. The seals are comprised of a material having volatile impurities. Resilient expanded silicone sponge material is utilized to either or both urge the apex seals and corner seals to their respective engaging surfaces; mechanical springs may be embedded in the sponge material for assisting the uniform nature of the resilient force of said sponge material. In one or both of said apex and corner seals, grooves are defined for receiving an embedment comprised of a friction smearable fluxing agent in the form of polyarylsulfone.

United States Patent Rao et a1.

1 1 RUBBING SEAL SYSTEM FOR A ROTARY COMBUSTION ENGINE {75] Inventors:Vemulapalli D. N. Rao, Woodhaven;

Yeshwant P. Telang, Grosse lle. both of Mich.

[73] Assignee: Ford Motor Company, Dcarborn,

Mich,

[221 Filed: Aug. 24. 1973 [21] Appl. N01: 391,375

[51] Int. C1....F01c19/02;F04c 27/00; FOlc 21/00 [58] Field of Search418/113, 120-123.

156] References Cited UNITED STATES PATENTS 409,800 8/1889 Owen 418/1132,268,868 l/1942 Given H 277/227 3,102,518 9/1963 Anderson 418/1203,130,964 4/1964 Johnson 1 i 1 1 i 267/152 3,161,350 12/1964 Lorcher 1 11 418/122 3,194,488 7/1965 Fuhrmann.... 418/113 3,196,849 7/1965 Paschke418/121 3,268,157 8/1966 Frcnzcl 418/122 3,289,649 12/1966 Lamm 418/1783,756,754 9/1973 Sakamaki 418/113 3,761,207 9/1973 Seidl 418/121 Zia.[/8

1 June 17,1975

FOREIGN PATENTS OR APPLICATIONS 1.116.951 11/1961 Germany 418/122Primary Examiner-John J. Vrablik Attorney, Agem, or I-irm-Joseph W.Malleck; Keith L, Zerschling [57] ABSTRACT A sealing assembly isdisclosed for use in providing a dynamic seal between a rotor and thesurrounding housing of a rotary internal combustion engine. An apex sealof considerable height is arranged to fit within a first receptacle inat least one location along the periphery of the rotor; the apex sealhas a transverse opening separating the body of the seal into first andsecond support portions. A second receptacle is defined about the endsof the first receptacle for receiving a corner seal adapted to engagethe side housing. The seals are comprised of a material having volatileimpurities. Resilient expanded silicone sponge material is utilized toeither or both urge the apex seals and corner seals to their respectiveengaging surfaces; mechanical springs may be embedded in the spongematerial for assisting the uniform nature of the resilient force of saidsponge material. In one or both of said apex and corner seals, groovesare defined for receiving an embedment comprised of a friction smearablefluxing agent in the form of polyarylsulfonei 19 Claims, 12 DrawingFigures PATENTEDJUN 17 I975 SHEET F'lG.9

F'IGLIZ RUBBING SEAL SYSTEM FOR A ROTARY COMBUSTION ENGINE BACKGROUND OFTHE INVENTION A highly efficient gas-tight seal between the apex sealsand rotor housing ofa typical rotary internal combustion engine isdifficult to obtain. The problem is principally due to the typical shapeof the rotor housing (epitrochoid) and the offset journalling of therotor providing for planetary movement. As a result, variable dynamicloads are imposed upon the apex seal during a complete revolution, thepeak loading being extremely high relative to loading in other regionsof the path. Gas pressure from the combustion chamber has been utilizedto urge the apex seal radially outwardly to accommodate the varyingcontour of the rotor housing and the varying inertial loads applied tothe apex seal. This has only been partly successful since shifting ofthe seal within its receptacle is required. A more uniform form ofloading is desirable.

The composition, of which the apex and corner seals are constructed,present another unique problem in that most compositions incur acyclical variation of their coefficient of friction during normaloperation. For example, those seals which have been formed fromcommercial graphite exhibit a dry rubbing friction vari ation which isexplained in part by a moisture-free dry environment at temperaturesabove 400450F. Initially the low friction of the graphite is attributedto occluded impurities which may be natural or synthesized in thegraphitic material. These impurities allow the graphitic material toglide easily under an applied tangcntial stress such as experiencedduring the rubbing application of the seals thereby permitting thecrystallites to obtain a favorable orientation resulting in lowfriction.

As the higher temperatures of operation are reached, the impuritiesevaporate eventually resulting in a return to a high coefficient offriction. When the surface layer is worn off, the coefficient offriction again drops due to the exposure of another incremental layer ofgraphitic material containing again the impurities. The duration of thecycle of variance in the coefficient of friction depends upon theoperating temperature achieved.

SUMMARY OF THE INVENTION A primary object of this invention is toprovide a simple and reliable sealing assembly for use in providing agas-tight dynamic seal in a typical rotary internal combustion engine;the assembly should be easy to manufacture and assemble, yet capable ofefficient operation under more severe operating conditions at higherspeeds than seal assemblies now in use.

Another object of the invention is to provide a material design for thesealing structure which has improved dry lubrication qualities andovercomes the incidents of cyclic variation of friction during dynamicsealing.

Another object of the invention is to provide a sealing assembly whichachieves a more uniform loading condition for the seal elementsconstituting the assembly, the uniform loading particularly optimizingthe loading at high speeds thereby resulting in improved sealingefficiency and extended life for the seals.

Particular features pursuant to the above objects comprise the use ofpolyarylsulfones (such as Astrel or Bakelite) as a seal embedment orapplication to a contacting surface. A metal oxide-fluoride material mayalso be used if unusually high temperatures are encountered. The sealbody material normally contains volatile impurities which wouldevaporate under temperature of frictional operation experienced by theseal structure; the embedment or application is arranged to flux thesurface and prevent premature volatization of such impurities exceptunder a controlled condition, thereby resulting in a decrease in thecyclic variation of friction. Another feature is the use ofa resilientsilicone sponge material interposed between the rotor and seals(including the apex and corner seals) in a manner to urge at least oneof the seals into dynamic engagement with the housing. The resilientmaterial thereby maintains a more uniform loading under the inertialforce variations of the rotor.

SUMMARY OF THE DRAWINGS FIG. I is an enlarged sectional view of aportion of a typical rotary internal combustion engine, illustrating thesealing assembly ofthis invention in a preferred embodiment;

FIG. 2 is a view similar to FIG. 1 illustrating a different arrangementof elastic material;

FIGS. 3-5 represent alternative perspective views in a schematic mannerof embedments utilized for the apex or corner seals;

FIG. 6 is an enlarged schematic illustration of the microstructure ofmaterial utilized for the seals of this invention but without the use ofembedments; a layer of graphite crystallites are oriented for easy glideand low friction under shear stress against a mating surface, such asthe housing:

FIG. 7 is a schematic view similar to that in FIG. 6 showing therearrangement of the microstructure as a result of the use of fluxingembedments;

FIG. 8 is a fragmentary end view of the sealing assembly showing thecorner seal in operation about the apex seal;

FIG. 9 shows an alternative embodiment illustrating a mechanical assistspring which is effective to apply biasing force not only in a directionradially outwardly but in a side thrust direction.

FIG. 10 is an enlarged schematic illustration of another alternativesealing assembly wherein the resilient material is utilized to imposeboth a force in a radially outward direction as well as in a sidewaysdirection to simultaneously urge the apex and corner seals into properengagement;

FIG. 11 is a view similar to that in FIG, 10 showing the use of anassist spring; and

FIG. 12 is a view similar to FIGS. 10 and I1 illustrating the forcesthat are exerted in the embodiments.

DETAILED DESCRIPTION Turning now to the figures, particularly FIG. 1,there is shown a preferred embodiment which is effective to achieve thedual objects of providing a superior dry lubricating characteristic forthe sealing assembly and at the same time optimize seal loading at highengine speeds. The sealing assembly (comprised of elements A through F)is adapted to provide a dynamic seal between a rotor 19 and a housing10, the housing having a typical epitrochoidally shaped end wall llapresented by a rotor housing portion 11. Side wall portions 12 and 13present flat inwardly facing side walls and I30 respectively. Thesealing assembly elements include receptacle A (formed as a slotextending across one of th apices of the triangular-shaped rotor l9).receptacles ll defined at the ends of each of the receptacles A. apexseal means C is disposed in each of the receptacles A and corner sealmeans D is disposed in each of the receptacles B. Resilient spongematerial E is provided in the spaces between the rotor and apex orcorner seal means to provide a uniform loading characteristic.Embedments F are provided in at least the apex seal means for promotinga smearing or fluxing condition to enhance the dry lubrication of theseal material.

ln more particularity. receptacle A is defined as a slot 25 (FIG. 8)having a width 40 (FIG. 8) and has a longitudinal extent substantiallycommensurate with the width l8 of rotor 1'). Slot 25 has a bottom wall250 against which the resilient material E bears for exerting a radialloading force against the apex seal means. The receptacle 8 is formed asa round recess 26 at each side of the rotor 19; each recess is arrangedto surround the ends of each receptacle A. The inner most portion ofeach receptacle B provides an alignment surface 26a for maintaining thecorner seal parallel with respect to the side wall surfaces 13a and 12a.

Each of the apex seal means comprise a slug or body of material 14having a generally elongated extent ef fective to fit within the slot 25and having opposite ends 140 and 14b in close proximity to the walls 12aand 13a. preferably in light engagement; a crown portion [4c of the bodyis adapted to engage the inner epitro choid wall lla of the rotorhousing. The body 14 has a substantial height 80 (FIG. 8); a transverseopening 81 separates the body into supporting portions 82 and 22. Body14 may have recesses 15 and 36 to define steps distinct from the bottom17 thereof.

The material of body 14 is comprised of a form of graphite and shouldhave a high hardness at high elevated temperatures; the minimum hardnessof the wear body should be at least R.- 30 at about 400F. Mostcommercial graphite, as well as standard graphite contain a high contentof volatile impurities. Standard graphite and commercial graphitesexhibit the incidents of cyclical friction in dry rubbing sealapplications due to the moisture-free dry environment at tem peraturesabove 400450F. The low friction of the graphite is attributed to theimpurities between the graphite crystallite layers. Significantly.water. as one of these impurities, facilitates easy glide under an applied tangential stress such as the rubbing of the seal against therotor housing. Crystallites are permitted to attain a favorableorientation resulting in low friction. At high temperatures, however.the evaporation of the impurities still occurs. eventually resulting inthe increase of friction. When the surface layer is worn off, frictiondrops again due to the availability of the impurities in the freshlyexposed layers. The duration of the cycle depends upon the attainedtemperature and the cycle decreases rapidly with an increasing attainedtemperature. For special graphites. synthesized with hygroscopic salts,the water of hydration in the salts is released at higher temperaturesfacilitating easy glide. But even in these graphites the evaporation andloss of impurities is quite rapid.

The corner seals 20 and 21 are shaped to fit about the ends of the apexseal and to the depth of the receptacle B. Each of the corner seals havean extension (20 and 210 respectively) which project into the opening 81of the apex seal and provide a means for urging the corner seal intoengagement with the ends of the apex seal. To

4 rigidify each of the corner seals. a nose (3i and 33 re spectfully) isprovided on the corner seals and adapted to lit within openings (32 and34 respectively) in the rotor housing at the back of receptacles B. SDry-lubrication The embedment F comprises one or more strips or depositsofmatcrial (see FIGS. 35) within recesses 42 in the crown portion of thebody M. The embedments are separated and are comprised of a materialwhich is H) designed to distribute across the major portion of the crownl4a under frictional forces to pack the pores of the body 14 and preventnon-uniform loss of volatiles (dry lubricants). The embedments must bearranged to replinish the outermost exposed layers of the embedl5 mentsas they are frictionally worn away or smeared during successive wearcycles of the body. The embedments are comprised of a polyarysulfonefluxing material which decomposes at or above 550F. Polyarysulfones,such as Astrel or Bakelite P-l300, may further contain additives of upto 40% graphite and 20% boron nitride. A metal or metal oxide'fluoride(such as copper-fluoride with 9% sodium fluoride and l 1% lithiumfluoride) may be used if the expected engine operating temperature isparticularly high and should be applied to the housing for achievingcomparable results. The friction smearable material may alternatively beapplied as a slurry to the crown surface of the apex seal or even to therotor housing; the latter will afford some degree of reducing the cycliccoefficient of friction but will not be as great as by the use of anembedment.

The embedments may be defined in various configurations to meet therequirement of adequate location for uniform smearing or fluxing. Theillustration in FIG. 4 represents approximately the embedments used inFIG. 1; rectangular strips 41 are embedded in recesses 42. However,embedments 43 may be arranged on a bias as that shown in FIG. 3, or theymay be provided with a V-shaped cross section 44 as that shown in FIG. 5(the widest part of the V being at the outermost exposed surface of theembedment).

As shown in FIG. 6. an apex seal composition is shown having no fluxingembedments. The loads expe rienced by the seal will result fromcentrifugal forces and the friction between the seal and the rotorhousing. The interface temperature increases with increasing enginespeed due to the increased centrifugal forces and the increased surfacespeed. Conventional graphite and metal impregnated graphite seals looselubricity; chatter begins as soon as the surface temperature exceeds500F. thereby resulting in very high seal wear and leakage. Even thoughthe crystallites are favorably orientated initially, because of thegliding action provided by the first impurities, the impurities begin tovolatize and certain of the favorably oriented crystallites will beremoved by wear. A randomly oriented crystallite will be substitutedthereby increasing friction.

To remedy this, and as shown in FIG. 7., embedment 41 provides a readysupply of fluxing polymer at the rubbing interface between the apex sealand the rotor housing 11. The polymer will, of course, smear 0r fluxacross the surface of both the rotor housing and the apex seal;quantities of the polymer will be squeezed into the porosity of the mainbody of the apex seal. thereby sealing off and preserving the impuritiesin the polymer which act as dry lubricants. Furthermore. the

favorably oriented crystallites adjacent the interface LII will bemaintained and not torn loose during rubbing action; this insures thatthe randomly oriented crystallites will be subsurface.

Uniform Loading Although the concept of utilizing a resilient means E ina single chamber is comprehended within this invention, as shown in FIG.9, opening 81 defining chamber 30 may also contain resilient means.Chamber 29 (between the bottom 25a of the slot 25 and the apex seal)receives sponge material to serve as a primary resilient means for theseals. The resilient means is comprised of an elastometer or expandedsilicone sponge material such as RTV silicone rubber produced by GE orDow Corning which cure at room temperature. Such silicone spongesconsist of polydimethyl siloxane and polymethyl phenyl siloxanes. Eachof these silicone sponges are capable of retaining elasticity attemperatures up to 500F for over 2,000 hours of use. The sponge materialexerts a uniform force both radially outwardly and sideways. Thus aforce is exerted against extensions 21a and 20a to retain the cornerseals tight against the ends of the apex seal; a sideways force is alsoexerted against the corner seals to in turn engage the side housings. Tosupplement the force of the sponge material, mechanical springs 23 and24, of convoluted configuration, are utilized. Spring 24 acts betweenthe base of receptacle A and the auxiliary apex seal; spring 23 actsbetween the opening in the apex seal and extensions 20a and 210. Spring24 acts as the primary pressurizing spring for the seals and spring 23acts as a pressure relief.

The embodiment of FIG. 2 illustrates the same seal assembly elements asin FIG. 1. except that the uniform loading is provided by a thin coating60 of elastomer sealant between the engaging surfaces of the corner andapex seal means. There is no sponge material in chambers 29 and 30.Spring 24 performs as the primary resilient means to obtain sealengagement with the housing.

In FIGS. and 11, embodiments are illustrated which further expand theuse of the silicone sponge 71 to act as biasing force for side seals 70which are annularly arranged on the sides of the rotor 72. The spongematerial surrounds an extension 73 of the corner seal and projectsbetween the end of the apex seal 75 and the slot 76 in the corner seal78. Thus, a greater bulk adhesive sealant is used between the corner andapex seals. Thus chatter of the apex seal will not affect the peformanceof the corner seal. FIG. It) differs from 11 in that the primary apexseal spring 77 is not present. In FIG. 12, the reaction forces(designated by arrows), generating a seal load on the apex and cornerseals, are illustrated.

FIG. 9 represents another alternative embodiment whereby the embedments61 extend transversely across the surface of the graphite apex seal 62to promote a smear distribution 66. The sponge material 63 contains asingle spring 64 which is arranged to exert a force not only radiallyoutwardly directly against the bottom of the apex seal 62, but also hasend portions 640 which exert a side thrust against comer seals 65 toaugument the resiliency of the sponge material.

The advantages of the above sealing assembly as shown in variousembodiments, comprise among others, (a) simplified assembly due to onestep curing of the sponge or sealant, (b) permits use of conventionalmaterials for the housing, such as cast iron or alumi num in the as-castcondition. (c) higher engine compression ratios can be achieved due tobetter sealing a higher speeds and (d) high temperature metal-fluorides(850-900F) as the sponge material opens up the possibility of an aircooled rotary engine.

5 We claim as our invention:

1. A sealing element carried by a rotor in a rotor housing of a rotaryinternal combustion engine comprising:

a. a wear-resistant body comprised of a composition which will maintainhigh hardness at elevated temperatures and contains volatile impurities,

b. a plurality of separated embedments disposed in said body andadjacent to at least one surface of said body which is adapted forfrictional engage.- ment with said rotor housing, the embedments beingcomprised of a material effective to be distributed across majorportions of said one surface under the influence of frictional forcesand effective, when so distributed to pack the pores of said body toprevent non-uniform loss of said impurities, said embedments beingarranged so that the distributed material can be replenished duringsuccessive wear cycles of the body.

2. The assembly as in claim 1, in which the rotor and side housings arecomprised of as-cast materials selected from the group consisting ofaluminum and cast iron, said apex and corner seal means being effectiveto interengage the as-cast surface of said housings.

3. A sealing element as in claim 1, in which said body is comprised ofgraphite.

4. A sealing element as in claim 1, in which the body consists ofamaterial having a hardness value of at least R. 30 at 400F, saidembedment consisting of a material having a decomposition temperature ofat least 550F.

5. A sealing element as in claim 4, in which the embedment consists of apolyarlsulfone having a decomposition temperature at least 600F.

6. A sealing element as in claim 5, in which the polyarlsulfone hasfiller material selected from the group consisting of fine graphitepowder and boron nitride.

7. The sealing element as in claim 4, which said embedment materialconsists of an admixture of metal oxide and fluoride having adecomposition temperature in the range of 850900F.

8. The sealing element as in claim 7, in which said ad mixture consistsof 80% copper oxide, 9% sodium fluoride, and 11% lithium fluoride.

9. A sealing assembly for use between a rotor and the surrounding rotorhousing and side housings of a rotary internal combustion engine, theassembly comprising:

a. a slotted receptacle in at least one location of said rotor,

b. apex seal means disposed in said slotted receptacle effective toprimarily interengage at an area with said rotor housing, and

c. high temperature mechanical resilient means biasing said apex sealmeans to effect said engagement under uniform loading across saidinterengaging area, said resilient means consisting of expandedsilicones which maintain elasticity up to at least 500F.

10. A sealing assembly for use in providing a gas-tight dynamic sealbetween a rotor and a rotor housing of a rotary internal combustionengine, the housing having side and end wall portions. the assemblycomprising:

a. a receptacle in at least one location of said rotor periphery,

b. an apex seal and a corner seal disposed in said receptacle. saidcorner seal being effective to move relative to the rotor along a linepassing away from said receptacle toward the housing end wall. said apexseal having a central transverse opening extending internally throughsaid seal. and

c. resilient means disposed in the space defined be tween saidreceptacle bottom and apex seal and in the opening. said resilient meanscooperating to uniformly urge both said apex seal radially outwardly andurge the corner seal along said line for effecting interengagement ofthe corner seal with the end wall.

H. The assembly as in claim it), in which the resilient means iscomprised of silicone expanded sponge material having a temperaturestability at least to 500F.

12. The assembly as in claim 10. in which the apex seal and corner sealare both comprised of a material selected from the group consisting ofgraphite having volatile impurities. and high temperature metallic alloys having volatile dry lubricant impurities distributed throughout 13.The assembly as in claim 10. in which at least one of said spacescontaining said resilient means has a mechanical spring embedded thereinto assist the resilient force acting upon said seals.

M. The assembly as in claim 10, in which said rotor has anotherreceptacle surrounding the end of said first 8 receptacle. said cornerseal being disposed in said another receptacle adapted to sea] with thehousing side portion as well as with the ends of said apex seal means,said corner seal having an extension acting as a bearing between saidresilient means and apex seal.

15. The assembly as in claim 10, in which said apex seal has at leastone groove in that portion of the surface adapted to engage the end wallportion. and a polymer-based embedment in said one groove effective tocyclically flux into the pores of said outer apex seal in response towear for cyclically decreasing the friction coefficient thereof.

16. The assembly as in claim 15, in which the polymer base flux containsat least one filler material selected from the group consisting of finegraphite powder. and boron nitride powder.

17. The assembly as in claim 15, in which said one groove extendssubstantially on a bias to the elongated extent of said seal.

18. The assembly as in claim 15, in which the apex seal is defined as anelongated strip extending substantially transversely across the width ofsaid rotor, and said one groove extending substantially parallel to theelongated extent of said apex seal.

19. The assembly as in claim 18, in which said groove has substantiallya V-shaped cross section, the widest part of said V being disposed atthe exposed surface of said groove.

1. A sealing element carried by a rotor in a rotor housing of a rotaryinternal combustion engine comprising: a. a wear-resistant bodycomprised of a composition which will maintain high hardness at elevatedtemperatures and contains volatile impurities, b. a plurality ofseparated embedments dispoSed in said body and adjacent to at least onesurface of said body which is adapted for frictional engagement withsaid rotor housing, the embedments being comprised of a materialeffective to be distributed across major portions of said one surfaceunder the influence of frictional forces and effective, when sodistributed to pack the pores of said body to prevent nonuniform loss ofsaid impurities, said embedments being arranged so that the distributedmaterial can be replenished during successive wear cycles of the body.2. The assembly as in claim 1, in which the rotor and side housings arecomprised of as-cast materials selected from the group consisting ofaluminum and cast iron, said apex and corner seal means being effectiveto interengage the as-cast surface of said housings.
 3. A sealingelement as in claim 1, in which said body is comprised of graphite.
 4. Asealing element as in claim 1, in which the body consists of a materialhaving a hardness value of at least Rc 30 at 400*F, said embedmentconsisting of a material having a decomposition temperature of at least550*F.
 5. A sealing element as in claim 4, in which the embedmentconsists of a polyarlsulfone having a decomposition temperature at least600*F.
 6. A sealing element as in claim 5, in which the polyarlsulfonehas filler material selected from the group consisting of fine graphitepowder and boron nitride.
 7. The sealing element as in claim 4, whichsaid embedment material consists of an admixture of metal oxide andfluoride having a decomposition temperature in the range of 850*-900*F.8. The sealing element as in claim 7, in which said admixture consistsof 80% copper oxide, 9% sodium fluoride, and 11% lithium fluoride.
 9. Asealing assembly for use between a rotor and the surrounding rotorhousing and side housings of a rotary internal combustion engine, theassembly comprising: a. a slotted receptacle in at least one location ofsaid rotor, b. apex seal means disposed in said slotted receptacleeffective to primarily interengage at an area with said rotor housing,and c. high temperature mechanical resilient means biasing said apexseal means to effect said engagement under uniform loading across saidinterengaging area, said resilient means consisting of expandedsilicones which maintain elasticity up to at least 500*F.
 10. A sealingassembly for use in providing a gas-tight dynamic seal between a rotorand a rotor housing of a rotary internal combustion engine, the housinghaving side and end wall portions, the assembly comprising: a. areceptacle in at least one location of said rotor periphery, b. an apexseal and a corner seal disposed in said receptacle, said corner sealbeing effective to move relative to the rotor along a line passing awayfrom said receptacle toward the housing end wall, said apex seal havinga central transverse opening extending internally through said seal, andc. resilient means disposed in the space defined between said receptaclebottom and apex seal and in the opening, said resilient meanscooperating to uniformly urge both said apex seal radially outwardly andurge the corner seal along said line for effecting interengagement ofthe corner seal with the end wall.
 11. The assembly as in claim 10, inwhich the resilient means is comprised of silicone expanded spongematerial having a temperature stability at least to 500*F.
 12. Theassembly as in claim 10, in which the apex seal and corner seal are bothcomprised of a material selected from the group consisting of graphitehaving volatile impurities, and high temperature metallic alloys havingvolatile dry lubricant impurities distributed throughout.
 13. Theassembly as in claim 10, in which at least one of said spaces containingsaid resilient means has a mechanical spring embedded therein to assistthe resilient force acting upon saId seals.
 14. The assembly as in claim10, in which said rotor has another receptacle surrounding the end ofsaid first receptacle, said corner seal being disposed in said anotherreceptacle adapted to seal with the housing side portion as well as withthe ends of said apex seal means, said corner seal having an extensionacting as a bearing between said resilient means and apex seal.
 15. Theassembly as in claim 10, in which said apex seal has at least one groovein that portion of the surface adapted to engage the end wall portion,and a polymer-based embedment in said one groove effective to cyclicallyflux into the pores of said outer apex seal in response to wear forcyclically decreasing the friction coefficient thereof.
 16. The assemblyas in claim 15, in which the polymer base flux contains at least onefiller material selected from the group consisting of fine graphitepowder, and boron nitride powder.
 17. The assembly as in claim 15, inwhich said one groove extends substantially on a bias to the elongatedextent of said seal.
 18. The assembly as in claim 15, in which the apexseal is defined as an elongated strip extending substantiallytransversely across the width of said rotor, and said one grooveextending substantially parallel to the elongated extent of said apexseal.
 19. The assembly as in claim 18, in which said groove hassubstantially a V-shaped cross section, the widest part of said V beingdisposed at the exposed surface of said groove.